Lock devices and key devices are evolving from the traditional pure mechanical locks. These days, there are wireless interfaces for electronic lock devices, e.g. by interacting with a portable key device. Such interaction can even occur without user interaction, e.g. with a portable key device being located in a pocket or handbag. However, in such a situation, there is a risk that someone on the inside unlocks the lock device by simply walking by the lock device. In order to prevent this from happening, without introducing user interaction to open the lock device, there needs to be a way to determine whether a portable key device is on the inside or on the outside. In this way, automatic access control could be disabled for inside devices, preventing inadvertent unlocking.
US 2012/0234058 discloses a wireless access control system including a lock. The lock includes an interior facing directional antenna and an external facing directional antenna. Each is operatively coupled to wireless communication circuitry to send signals to, and list for signals from, remote access device. If remote access device is interior of the lock, then interior facing directional antenna communicates with remote access device, and the signal strength sensed by directional antenna will be greater than the signal strength sensed by directional antenna (which may be no sensed signal). Lock, and in turn system, determine that remote access device is inside the home, dwelling or structure.
However, such a determination of position based on dual antenna signals has proven to be unreliable. This is due to radio signals being distorted by reflections and fading which depends on external objects and interference, which can not be reliably controlled.